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Accelerometer Shake in Android

TheWholeMushroomBarTheWholeMushroomBar
edited April 2014 in Android Mode

Hi,

I'm working on a small drawing project in processing android mode where i'd like the user to be able to shake the device to clear the screen.

I'm working off the Sensors -> Accelerometer example in processing and i have managed to get the accelerometer to control movement on screen in another sketch. I can't quite figure out how to implement sense that the user is shaking the device.

This is the example code from processing: Accelerometer.pde:

AccelerometerManager accel;
float ax, ay, az;


void setup() {
  accel = new AccelerometerManager(this);
  orientation(PORTRAIT);
  noLoop();
}


void draw() {
  background(0);
  fill(255);
  textSize(70);
  textAlign(CENTER, CENTER);
  text("x: " + nf(ax, 1, 2) + "\n" + 
       "y: " + nf(ay, 1, 2) + "\n" + 
       "z: " + nf(az, 1, 2), 
       0, 0, width, height);
       shakeEvent(10);
}


public void resume() {
  if (accel != null) {
    accel.resume();
  }
}


public void pause() {
  if (accel != null) {
    accel.pause();
  }
}


public void shakeEvent(float force) {
  println("shake : " + force);
}


public void accelerationEvent(float x, float y, float z) {
//  println("acceleration: " + x + ", " + y + ", " + z);
  ax = x;
  ay = y;
  az = z;
  redraw();
}

AccelerometerManager.Java

import java.lang.reflect.*;
import java.util.List;

import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;


/**
 * Android Accelerometer Sensor Manager Archetype
 * @author antoine vianey
 * under GPL v3 : http://www.gnu.org/licenses/gpl-3.0.html
 */
public class AccelerometerManager {
  /** Accuracy configuration */
  private float threshold = 0.2f;
  private int interval = 1000;

  private Sensor sensor;
  private SensorManager sensorManager;
  // you could use an OrientationListener array instead
  // if you plans to use more than one listener
//  private AccelerometerListener listener;

  Method shakeEventMethod;
  Method accelerationEventMethod;

  /** indicates whether or not Accelerometer Sensor is supported */
  private Boolean supported;
  /** indicates whether or not Accelerometer Sensor is running */
  private boolean running = false;

  Context context;


  public AccelerometerManager(Context parent) {
    this.context = parent;

    try {
      shakeEventMethod =
        parent.getClass().getMethod("shakeEvent", new Class[] { Float.TYPE });
    } catch (Exception e) {
      // no such method, or an error.. which is fine, just ignore
    }

    try {
      accelerationEventMethod =
        parent.getClass().getMethod("accelerationEvent", new Class[] { Float.TYPE, Float.TYPE, Float.TYPE });
    } catch (Exception e) {
      // no such method, or an error.. which is fine, just ignore
    }
//    System.out.println("shakeEventMethod is " + shakeEventMethod);
//    System.out.println("accelerationEventMethod is " + accelerationEventMethod);
    resume();
  }


  public AccelerometerManager(Context context, int threshold, int interval) {
    this(context);
    this.threshold = threshold;
    this.interval = interval;
  }


  public void resume() {
    if (isSupported()) {
      startListening();
    }
  }


  public void pause() {
    if (isListening()) {
      stopListening();
    }
  }


  /**
   * Returns true if the manager is listening to orientation changes
   */
  public boolean isListening() {
    return running;
  }


  /**
   * Unregisters listeners
   */
  public void stopListening() {
    running = false;
    try {
      if (sensorManager != null && sensorEventListener != null) {
        sensorManager.unregisterListener(sensorEventListener);
      }
    } 
    catch (Exception e) {
    }
  }


  /**
   * Returns true if at least one Accelerometer sensor is available
   */
  public boolean isSupported() {
    if (supported == null) {
      sensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);
      List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ACCELEROMETER);
      supported = new Boolean(sensors.size() > 0);
    }
    return supported;
  }


//  /**
//   * Configure the listener for shaking
//   * @param threshold
//   *          minimum acceleration variation for considering shaking
//   * @param interval
//   *          minimum interval between to shake events
//   */
//  public static void configure(int threshold, int interval) {
//    AccelerometerManager.threshold = threshold;
//    AccelerometerManager.interval = interval;
//  }


  /**
   * Registers a listener and start listening
   * @param accelerometerListener callback for accelerometer events
   */
  public void startListening() {
//    AccelerometerListener accelerometerListener = (AccelerometerListener) context;
    sensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);
    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ACCELEROMETER);
    if (sensors.size() > 0) {
      sensor = sensors.get(0);
      running = sensorManager.registerListener(sensorEventListener, sensor, SensorManager.SENSOR_DELAY_GAME);
//      listener = accelerometerListener;
    }
  }


//  /**
//   * Configures threshold and interval
//   * And registers a listener and start listening
//   * @param accelerometerListener
//   *          callback for accelerometer events
//   * @param threshold
//   *          minimum acceleration variation for considering shaking
//   * @param interval
//   *          minimum interval between to shake events
//   */
//  public void startListening(int threshold, int interval) {
//    configure(threshold, interval);
//    startListening();
//  }


  /**
   * The listener that listen to events from the accelerometer listener
   */
  //private static SensorEventListener sensorEventListener = new SensorEventListener() {
  private SensorEventListener sensorEventListener = new SensorEventListener() {
    private long now = 0;
    private long timeDiff = 0;
    private long lastUpdate = 0;
    private long lastShake = 0;

    private float x = 0;
    private float y = 0;
    private float z = 0;
    private float lastX = 0;
    private float lastY = 0;
    private float lastZ = 0;
    private float force = 0;

    public void onAccuracyChanged(Sensor sensor, int accuracy) {
    }

    public void onSensorChanged(SensorEvent event) {
      // use the event timestamp as reference
      // so the manager precision won't depends 
      // on the AccelerometerListener implementation
      // processing time
      now = event.timestamp;

      x = event.values[0];
      y = event.values[1];
      z = event.values[2];

      // if not interesting in shake events
      // just remove the whole if then else bloc
      if (lastUpdate == 0) {
        lastUpdate = now;
        lastShake = now;
        lastX = x;
        lastY = y;
        lastZ = z;

      } else {
        timeDiff = now - lastUpdate;
        if (timeDiff > 0) {
          force = Math.abs(x + y + z - lastX - lastY - lastZ) 
            / timeDiff;
          if (force > threshold) {
            if (now - lastShake >= interval) {
              // trigger shake event
//              listener.onShake(force);
              if (shakeEventMethod != null) {
                try {
                  shakeEventMethod.invoke(context, new Object[] { new Float(force) });
                } catch (Exception e) {
                  e.printStackTrace();
                  shakeEventMethod = null;
                }
              }
            }
            lastShake = now;
          }
          lastX = x;
          lastY = y;
          lastZ = z;
          lastUpdate = now;
        }
      }
      // trigger change event
//      listener.onAccelerationChanged(x, y, z);
      if (accelerationEventMethod != null) {
        try {
          accelerationEventMethod.invoke(context, new Object[] { x, y, z });
        } catch (Exception e) {
          e.printStackTrace();
          accelerationEventMethod = null;
        }
      }
    }
  };
}

I'm assuming i need to do something with this function in Accelerometer.pde

    public void shakeEvent(float force) {
      println("shake : " + force);
    }

But I'm not quite sure what to do. Some help would be appreciated.

Thanks!

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